Method and apparatus for starting an engine having a turbocharger

ABSTRACT

A system ( 40 ) for starting an internal combustion engine ( 12 ) of an automotive vehicle ( 10 ) has a controller ( 54 ) coupled to a starter/alternator ( 42 ). The engine ( 12 ) has a crankshaft ( 50 ) and a turbocharger ( 24 ). The controller ( 54 ) initiates the starting of the engine ( 12 ) by rotating the crankshaft ( 50 ). The rotating crankshaft ( 50 ) displaces an amount of air from the cylinders ( 14 ) of the engine ( 12 ) to rotate the rotor shaft of the turbocharger ( 21 ). The turbocharger ( 25 ) thus draws in air, compresses the air and provides the compressed air to the cylinders ( 14 ). When the engine is started the initial power is increased due to the compressed air.

TECHNICAL FIELD

The present invention relates generally to internal combustion enginesfor automotive vehicles, and more specifically, to an automotive vehiclehaving a starter/alternator and a turbocharger coupled to the engine.

BACKGROUND

Automotive vehicles with internal combustion engines are typicallyprovided with both a starter motor and alternator. In recent years, acombined alternator and starter motor has been proposed. Such systemshave a rotor mounted directly to the crankshaft of the engine and astator sandwiched between the engine block and the bell housing of thetransmission. During initial startup of the vehicle, thestarter/alternator functions as a starter. While functioning as astarter, the starter/alternator rotates the crankshaft of the enginewhile the cylinders are fired.

After the engine is started, the starter/alternator is used as agenerator to charge the electrical system of the vehicle.

Many vehicles have turbochargers incorporated with the engine. Theseturbochargers are commonly referred to as exhaust-gas turbochargers. Aturbocharger consists of two machines: a turbine and a compressormounted on a common shaft. The turbine is coupled to the exhaust systemand uses the energy obtained in the flow of the exhaust system to drivethe compressor. The compressor in turn, draws in outside air, compressesit and supplies it to the cylinders. The compressed air increases thepower output of the engine.

Exhaust gas turbochargers operate using the mass flow of the exhaustgas. Thus, some time is associated with providing enough exhaust gas torotate the turbocharger at a sufficient speed to provide compression atthe output of the turbocharger. Such time is typically referred to asturbo lag. During turbo lag the engine output power is less than thatwhen the turbocharger is operating.

In foreseeable automotive applications, the engine may be shut downduring stops (e.g., red lights). When the accelerator is depressed, thestarter/alternator starts the motor and the engine will resume firing.Thus, many startups may occur over the course of a trip.

It would therefore be desirable to reduce the amount of turbo lag andthus increase the amount of power of the engine during startup.

SUMMARY OF THE INVENTION

It is therefore one object of the invention to increase the power outputof the engine during startup.

In one aspect of the invention, a method of controlling the starting ofan internal combustion engine having a starter coupled to the crankshaftof the engine and a turbocharger comprises the steps of: rotating theshaft of the turbocharger to a predetermined speed and starting theengine when the turbocharger reaches the predetermined speed.

In a further aspect of the invention, a system for an automotive vehiclecomprises an internal combustion engine having a crankshaft coupled topistons. A turbocharger has a rotor that is fluidically coupled to thepistons. A starter/alternator is coupled to the crankshaft of theengine. A controller is coupled to the starter/alternator to initiatethe rotation of the crankshaft to displace air from the pistons androtate the rotor of the turbocharger. The controller starts the engineupon the rotor reaching a predetermined speed.

One advantage is that power from the engine may be increased at startup.

Other objects and features of the present invention will become apparentwhen viewed in light of the detailed description of the preferredembodiment when taken in conjunction with the attached drawings andappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an automotive vehicle having astarter/alternator system according to the present invention.

FIG. 2 is a schematic view of a piston of the engine with a turbochargerfluidically coupled thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is described with respect to a particularconfiguration of a starter/alternator. However, the teachings of thepresent invention may be applied to various starters for internalcombustion engines.

Referring now to FIG. 1, an automotive vehicle 10 is illustrated havingan internal combustion engine 12 having cylinders 14 with pistons 16located therein. Each cylinder 14 is coupled to a fuel pump 18 through afuel injector (not shown) or other fuel delivery system. Each cylinder14 also has a spark plug 20 or other ignition source coupled to apowertrain control unit. A powertrain control unit 22 controls theignition timing and fuel pump operation 18 in a conventional mannersubject to the improvements of the present invention.

Engine 12 has a turbocharger 24 coupled to the exhaust system (shownbelow in FIG. 2) of engine 12. Thus, turbocharger 24 is commonlyreferred to as an exhaust gas turbocharger. Also, the present inventionapplies to superchargers as well. Turbocharger as used herein refers toboth.

Engine 12 is coupled to a transmission 26. Transmission 26 may beautomatic, manual or continuously variable. Transmission 26 is coupledto a differential 28 to drive an axle 30 to provide power to wheels 32.Of course, the present invention is also applicable to four wheel drivesystems in which all of the wheels 32 are driven. A starter/alternatorsystem 40 that includes a starter/alternator 42 and its associatedcontrol electronics is coupled to engine 12. In the present invention,starter/alternator 42 is positioned between a housing 44 of transmission26 and the engine 12. Starter/alternator 42 has a stator fixedlyattached to bell housing 44 and a rotor 48 coupled to a crankshaft 50 ofengine 12. A clutch 52 is used to engage and disengage engine 12 fromtransmission 26. As will be further described below, starter/alternator42 is used as a starter during engine startup and as an alternator tosupply power to recharge the batteries of the vehicle and to supplyelectrical loads. Clutch 52 allows starter/alternator 42 to start theengine prior to engagement of the transmission.

Starter/alternator system 40 has a system controller 54 that is coupledto powertrain control unit 22 and to a power inverter 56. In practice,the power inverter 56 and system controller 54 may be contained in asingle package. The inverter 56 is used to convert DC power to AC powerin the startup mode and AC power to DC power in power generation mode aswill be further described below.

Power inverter 56 is coupled to an energy storage device 58 such as anultra capacitor, a first DC to DC converter 60, and a second DC to DCconverter 62. DC to DC converter 60 is coupled to a 36 volt battery 64.DC to DC converter 62 is coupled to a 12 volt battery 66. Of course, theactual battery voltage is dependent on the particular system to which itis attached.

Referring now to FIG. 2, a turbocharger 24 is shown coupled to anexhaust system 70 of engine 12 with cylinders 14 and a piston 16. Onlyone cylinder 14 and piston 16 is shown for simplicity. Piston 16 iscoupled to crankshaft 50. Gasses are input and exhausted from cylinders14 by valves 71, 72, respectively. Although two valves are illustrated,the present invention applies to multi-valve engines. Turbocharger 24 isalso coupled to an air intake system 74. A waste gate 76 having a piston78 may be used to control the pressure into turbocharger 24 by divertingan amount of exhaust gas as is commonly known in the art. Waste gate 76is a bypass around turbocharger 24.

Turbocharger 24 has a common rotor shaft 80 that couples the turbineportion 82 to compressor portion 84 of turbocharger 24. As gasses movefrom within cylinder 14 through exhaust system 70, the turbine portion82 is caused to rotate which in turn through rotor shaft 80 causescompressor portion 84 to rotate. Compressor portion 84 draws in externalair through a filter element 86 of an air induction system andcompresses the air to force the air into cylinder 14. This compressioncauses the power output of engine to increase. However, the power is notincreased until a sufficient amount of airflow through exhaust system 70is established. In prior systems, the airflow was exhaust gasses.

In certain operating conditions of a motor vehicle, it may be desirableto provide a greater amount of power from engine upon startup. Thepresent invention is particularly applicable to systems in which theengine is completely shut down when the vehicle is at rest, such as at astop light. In such a system, upon immediate depression of theacceleration pedal a great amount of power is required. Thestarter/alternator provides the required power in a substantiallyshorter time then the engine firing.

In operation, the rotor shaft 80 of the turbocharger 24 is spun toprovide power upon startup of the vehicle. The rotor shaft 80 ofturbocharger 24 is rotated to a predetermined speed that allows thecompressor portion 84 to increase the power of the engine. The startingprocess of engine 12 is initiated by a key placed in the ignitionposition or the depression of the accelerator pedal (not shown).Thirty-six volt battery 64 provides electrical power forstarter/alternator 42 which is stepped up to 300 volts by DC to DCconverter 60. The 300 volts is used to charge energy storage 58.Inverter 56 converts the DC power to three-phase AC power. The AC poweris supplied to the stator 46 of starter/alternator 42. Thestarter/alternator 42 rotates rotor 48 which in turn rotates crankshaft50 of engine 12. During the startup process, the valves 71, 72 arealternately placed in the open position and closed position depending onthe position of the crankshaft which in turn is coupled to the camshaft(not shown) driving the valves. The rotation of crankshaft 50 and thusthe movement of the pistons 16 causes an amount of air to be displacedinto exhaust system 70.

The starter/alternator 42 is used to displace a sufficient amount of air(i.e., mass airflow) to turn rotor shaft 80 by rotation of the turbineportion 82 of turbocharger 24. The compressor portion 84 in turncompresses intake air and provides it to cylinder 14. As rotor shaft 80turns, the power input to engine 12 will be increased upon startup ofthe engine. When the rotor shaft 80 of turbocharger 24 reaches apredetermined speed, the engine 12 is started by supplying fuel throughfuel pump 16 and controlling the spark timing through spark plugs 20through powertrain control unit 22. Thus, as the engine is started, theturbocharger is increasing the power to engine 12. The speed of rotorshaft 80 may be measured directly by using a sensor 90 coupled to rotorshaft 80. Thus, upon rotor shaft 80 reaching a sufficient speed, thecontroller 54 may trigger the starting of the combustion process in theengine.

Another method for determining the approximate speed of rotor shaft 80is by inferring the speed by the amount of time that the engine and thusthe pistons 16 have been displacing air into the exhaust system 70.Because the cylinders 14 contain a predetermined volume, the volume andthus the mass airflow of air into the turbine portion 82 of turbocharger24 may be inferred. The time may be measured by system controller 54.

Once the turbo rotor is turning at a sufficient speed and the enginecombustion process is initiated, the starter/alternator 42 is used in agenerating mode. In the generating mode, the energy storage system 58,and batteries 64, 66 are monitored to determine whether they are fullycharged. If any of the energy storage sources drop below a predeterminedrange, three-phase power from starter/alternator 42 is converted to 300volts DC by power inverter 56. DC to DC converters 60, 62 are used toconvert the 300 volts DC to 42 volts and 14 volts respectively. Itshould be noted that the ultra capacitors of energy storage 58 arecharged directly by power converter 56.

While particular embodiments of the invention have been shown anddescribed, numerous variations and alternate embodiments will occur tothose skilled in the art. Accordingly, it is intended that the inventionbe limited only in terms of the appended claims.

What is claimed is:
 1. A method of controlling the starting of aninternal combustion engine having a starter starter/alternator coupledto the crankshaft of the engine and a turbocharger having a rotor, saidmethod comprising the steps of: rotating the crankshaft of the enginewith the starter/alternator; rotating the rotor of the turbocharger to apredetermined speed; and starting the engine when the turbochargerreaches the predetermined speed.
 2. A method as recited in claim 1wherein the step of rotating the rotor shaft comprises the step ofgenerating a mass airflow from the engine and coupling the mass airflowto said rotor shaft of the turbocharger.
 3. A method as recited in claim2 wherein the step of rotating the rotor shaft comprises rotating thecrankshaft of the vehicle with a starter starter/alternator and whereinthe step of generating a mass airflow comprises the step of displacingair by moving pistons coupled to the crankshaft.
 4. A method as recitedin claim 1 wherein the step of starting the engine comprises the step ofoperating the fuel pump; and providing fuel to cylinders of the engine.5. A method as recited in claim 1 further comprising the step ofdetermining the approximate speed of the rotor shaft of the turbochargerfrom the length of time that the crankshaft has been rotated.
 6. Amethod as recited in claim 1 further comprising the step of generatingpower from the starter starter/alternator after the step of starting theengine.
 7. A method of starting a vehicle with a starter, and aturbocharger and an internal combustion engine comprising the steps of:rotating the crankshaft of the engine with the starter; moving pistonsin a respective cylinder; displacing air into the exhaust system withthe piston; rotating a shaft of the turbocharger with the displaced airto a predetermined speed; and starting the engine when the turbochargerreaches the predetermined speed.
 8. A method as recited in claim 7wherein the step of rotating the rotor shaft comprises the step ofgenerating a mass airflow from the engine and coupling the mass airflowto said rotor shaft of the turbocharger.
 9. A method as recited in claim7 wherein the step of starting the engine comprises the step ofoperating the fuel pump; and providing fuel to cylinders of the engine.10. A method as recited in claim 7 further comprising the step ofdetermining the approximate speed of the rotor shaft of the turbochargerfrom the length of time that the crankshaft has been rotated.
 11. Amethod as recited in claim 7 further comprising the step of generatingpower from the starter after the step of starting the engine.
 12. Asystem for an automotive vehicle comprising: an internal combustionengine having a crankshaft coupled to pistons; a turbocharger having arotor shaft; a starter/alternator coupled to the crankshaft; acontroller coupled to the starter/alternator initiating the rotation ofsaid crankshaft to displace air from the pistons and rotate the rotorshaft of said turbocharger, said controller starting said engine uponthe rotor shaft reaching a predetermined speed.
 13. A system as recitedin claim 12 further comprising a fuel pump.
 14. A system as recited inclaim 13 wherein said controller operating said fuel pump duringstarting the engine.
 15. A system as recited in claim 12 wherein saidstarter is a starter/alternator.
 16. A system as recited in claim 12further comprising a speed sensor coupled to the shaft of theturbocharger.
 17. A system as recited in claim 12 further comprising apower inverter coupled to said starter.
 18. A system as recited in claim12 further comprising an energy storage device coupled to said powerinverter.